Bus duct firestop system

ABSTRACT

A firestop system for fire stopping a bus duct that passes through an opening in a marine deck or a marine bulkhead includes a boot seal wrapped around the bus duct housing. The boot seal has a top end attached to the bus duct, and a bottom end attached to the division. The boot seal is made of flexible material to allow for movement of the bus duct relative to the division due to vibration. The boot seal may be made of a thermal barrier wrap or other high-temperature insulating mat materials to allow heat generated under normal condition to escape while providing firestopping and temperature resistance under fire exposure conditions. The firestop system may also have a gasket positioned between the bus duct and the boot seal to accommodate irregularities in the outside surface of the bus duct housing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This present application claims priority to International PatentApplication Serial No. PCT/US2017/033552 filed on May 19, 2017, whichclaims priority to U.S. Provisional Patent Application No. 62/339,214filed May 20, 2016, the disclosures of which are incorporated herein byreference in full.

FIELD OF THE INVENTION

This disclosure relates to the field of firestop system and particularlyfirestop system for bus duct penetrating through fire-rated divisions.

DESCRIPTION OF THE PRIOR ART

In marine construction, a bus bar enclosure, or a bus duct needs to befirestopped to comply with the International Maritime Organization (IMO)Fire Test Protocol (FTP) Code. When a bus duct penetrates through afire-rated division, such as bulkheads and decks, many existingfirestopping methods fail due to the vibration of the vessel. Forexample, vibrations may cause the sealant used in traditional methods tocrack. Further, because the bus duct is a metal housing that is made ofcopper or aluminum, it tends to get hot in a fire and existing firestopproducts tend to trap the heat inside the bus duct.

SUMMARY

A firestop system for fire stopping a bus duct that passes through anopening in a division includes a boot seal positioned to surround thebus duct. The boot seal has a first end positioned to surround andattach to the bus duct and a second end distal from the first end andpositioned to surround the bus duct and attach to the division. Thedivision may be a marine deck or a marine bulkhead. The boot seal ismade of flexible materials to allow for movement of the bus ductrelative to the division due to vibration. The boot seal is also made ofmaterials that allow for heat to escape during ambient conditions whileproviding firestopping and temperature resistance under fire exposureconditions. For example, the boot seal may be made of a thermal barrierwrap, such as microporous insulation material including at least aluminatrihydrate. The boot seal may also be made of high-temperaturefiberglass.

In some scenarios, each of the first end and second end of the boot sealdefines an opening and the opening of the second end is larger than theopening of the first end. The firestop system may also include a firstbracket positioned to surround the bus duct and attach the first end ofthe boot seal to the bus duct. The firestop system may have a gasketpositioned between the first bracket and the bus duct. The gasket may bemade of substantially intumescent foam gasket material.

The boot seal may include a sealable split extending from the first endof the boot seal to the second end of the boot seal to allow the bootseal to open and wrap around the bus duct for installation. In somescenarios, the sealable split may be closeable with a zipper that ismade of fire retardant materials. The boot seal may also include atoggle attached thereto proximate to the first end of the boot seal tosecure the boot seal to the bus duct.

The firestop system may also include a cover plate having a centralopening positioned to surround a cross-section of the bus duct andconfigured to attach the second end of the boot seal to the division.The cover plate can be made of steel. The firestop system may alsoinclude one or more weld tabs positioned to attach the cover plate tothe division. Alternatively, and/or additionally, the firestop systemmay have one or more clamps, each having a corresponding bolt positionedto go through an opening in the cover plate and an opening in thedivision and thread into the clamp so that the cover plate is attachedto the division.

Additionally, the firestop system may also include one of more boltattachments installed on the cover plate and positioned to attach aflange of the second end of the boot seal to the cover plate. Thefirestop system may further include a duct seal placed on the coverplate and positioned to cover the opening of the cover plate around thebus duct. The duct seal may also be locked to the cover place by one ormore lock tabs that are fixedly attached to the cover plate.

In some scenarios, the firestop system may also include a second bracketpositioned to attach the second end of the boot seal to the division.The second bracket may have an L-shaped cross-section formed by a firstportion positioned to be attached to the division and a second portionextending perpendicularly from the first portion and positioned toattach the second end of the boot seal thereto. Alternatively, and/oradditionally, the firestop system may further include a sleeveattachable to the division. The sleeve may be positioned to pass throughthe opening in the division. The sleeve may also have an opening thatallows the bus duct to pass through. When the sleeve is attached to thedivision, it allows the second bracket to attach thereto, which securesthe second end of the boot seal to the division.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a traditional bus duct firestop.

FIG. 2 illustrates an example of a marine bus duct firestop surroundingthe bus duct.

FIGS. 3A and 3B illustrate an example of a marine bus duct firestopsystem.

FIG. 4 illustrates an example of a marine bus duct firestop system.

FIG. 5 illustrates an example of a marine bus duct firestop system.

FIG. 6 illustrates an example of a boot seal with a sealable split inthe firestop system in FIG. 5.

FIG. 7A illustrates an example of a cover plate of the firestop systemin FIG. 5.

FIG. 7B illustrates an example of a clamp for locking the cover plate tothe division.

FIG. 7C illustrates an example of a duct seal in the firestop system inFIG. 5.

DETAILED DESCRIPTION

This disclosure is not limited to the particular systems, methodologiesor protocols described, as these may vary. The terminology used in thisdescription is for the purpose of describing the particular versions orembodiments only, and is not intended to limit the scope.

As shown in FIG. 1, a traditional bus duct firestop generally usesfire-resistant mineral wool batt insulation packing material 16 to fillin the space between the bus duct 20 and the fire-rated floor or wall12. The fire-rated floor or wall may be a deck or bulkhead in a maritimeconstruction. The traditional bus duct firestop system also has afirestop sealant 18 on top of the insulation material 16, and it may becovered by a steel cover plate 14. This traditional firestop system,however, may not be suitable for marine applications, in which vibrationoften results from the movement of the vessel. In marine applications,the sealant 18 may be prone to cracking due to the vibration. Further,the insulation material 16 is required to achieve temperature ratings,i.e. insulate the bus duct and reduce temperature transmission fromexposed to unexposed side. However, as the metal housing of the bus ductgets hot as result of a fire, the insulation material can prevent theheat from being released, and thus trap the heat built up in the busduct. When this happens, the current carrying capacity of the conductorsinside the bus duct is reduced or de-rated. As such, the traditionalfirestop system may even create a greater fire risk or de-rating of theelectrical bus bar. The bus duct firestop system described in thispatent disclosure is intended to solve the above mentioned issues and/orother issues.

As shown in FIG. 2, a firestop apparatus for fire stopping a bus duct 22that passes through an opening in a division 28, such as a floor or wallin maritime application, includes a boot seal 24 positioned to surroundthe bus duct 22. The boot seal has a first (top) end positioned tosurround and attach to the bus duct, and a second (bottom) end distalfrom the first end and positioned to surround the bus duct and attach tothe division. In some scenarios, the division may be a marine deck or amarine bulkhead. Each end of the boot seal 24 has an opening to surroundthe bus duct, and the opening of the bottom end is larger than that ofthe top end.

The boot seal may be made of flexible materials to allow for movement ofthe bus duct relative to the division due to vibration. The boot sealmay include an insulating material such as a thermal barrier wrap or ahigh-temperature glass fiber mat. These materials allow for heat toescape during ambient conditions while providing firestopping andtemperature resistance under fire exposure conditions. The thermalbarrier wrap is usually manufactured for use in large electrical panelsand gas valve stations installed in fire-rated construction, and mayprovide up to two hours of electrical circuit integrity ensuring circuitperformance even when consumed in flame. In one example, the thermalbarrier wrap of the boot seal may comprise a microporous insulationmaterial including at least alumina trihydrate. High-temperaturefiberglass may be widely available in various industries, such as thosemade with high quality E-Glass that will not burn and will withstandcontinuous exposure to temperatures at about 1000° F. to 1500° F. (540°C. to 800° C.). The boot seal may also be made of silicone coated glassfabric, such as those manufactured by Alpha Associates, Inc.

As shown in FIGS. 3A and 3B, the firestop system may include a bracket32 positioned to surround the bus duct 30 and attach the top end of theboot seal to the bus duct. For example, the bracket 32 may be positionedbetween the bus duct 30 and the boot seal 34, allowing the boot seal tobe fastened or screwed thereto. In some scenarios, the bracket 32 mayhave a shape that corresponds to the shape of the bus duct 30 to form aseal between the bus duct 30 and the bracket 32. The firestop system mayalso include a sealing gasket 36 positioned between the first bracketand the bus duct to conform to irregularities on the outside surface ofthe bus duct housing, such as seams and other projections, and perform aseal function. In some scenarios, the sealing gasket 36 may besubstantially of intumescent foam material or the like.

There can be various ways to attach the bottom end of the boot seal 34to the division 40. For example, the firestop system may also include anadditional bracket 38 positioned to attach the bottom end of the bootseal 34 to the division 40. The additional bracket 38 may have aL-shaped cross-section formed by a first (horizontal) portion positionedto be attached to the division and a second (vertical) portion extendingperpendicularly from the first portion and positioned to attach thesecond end of the boot seal thereto.

As shown in FIG. 4, the firestop system may also include a sleeve 54positioned to pass through the opening in the division, and the sleeve54 may also have an opening that allows the bus duct 42 to pass through,where the sleeve is attachable to the division 56. For example, thesleeve can be welded, or screwed, to the bulkhead or deck. The sleeve 54may also be configured to allow the second bracket 52 to attach theretoso that the bottom end of the boot seal 50 is secured to the division56.

The above illustrated embodiments can vary. For example, in a preferredembodiment, as shown in FIGS. 5-7, the firestop system may include aboot seal 60 positioned to surround the bus duct 58. The boot seal 58has two ends: the top end 66 and the bottom end 67 distal from the topend 66. The top end 66 is positioned to surround and attach to the busduct 58, whereas the bottom end 67 is positioned to surround the busduct 58 and attach to the division 72. The boot seal 60 can be made offlexible materials such that it allows for movement of the bus ductrelative to the division due to vibration. In a marine construction, thedivision may be a marine deck or a marine bulkhead. The materials forthe boot seal 60 can use the various embodiments illustrated above.

In FIG. 6, the boot seal 60 may include a sealable split 62 extendingfrom the top end 66 of the boot seal 60 to the bottom end 67 of the bootseal 60 to allow the boot seal 60 to open and wrap around the bus duct58 for installation. In some scenarios, the sealable split 62 may be azipper made of fire retardant materials. The boot seal 60 may furtherinclude a toggle 64 attached thereto proximate to the top end 66 of theboot seal 60. The boot seal 60 may be opened at the sealable split 62,wrapped around the bus duct 58, and sealed at the sealable split 62.Then the toggle 64 may be engaged to tighten the top end of the bootseal 60 so that it is secured around the bus duct 58. The attachment ofthe boot seal 60 to the division 72 will be further explained withreference to FIGS. 7A-7C.

In FIG. 7A, the firestop system may include a cover plate 70, which hasa central opening 98 positioned to surround a cross-section of the busduct 58. The cover plate 70 can be made of metal, such as steel, and itcan be configured to attach the bottom end of the boot seal to thedivision, which will be explained further. The firestop system mayfurther include one or more weld tabs 90 positioned to attach the coverplate 70 to the division 72. In some scenarios, the weld tabs 90 may bewelded to the division, and allow for the cover plate 70 to attachthereon. In other scenarios, the welded tabs 90 may be glued, screwed orattached using other means to the division 72. The illustratedattachment of the cover plate 70 to the division 72 provides thebenefits of vibration resistant and elimination the need for otherattachments.

In order to be installed around the bus duct 58, the cover plate 70 maybe split into multiple sections that join together. For example, thecover plate 70 may include two halves, which will be installedseparately and joined together surrounding the bus duct 58. In somescenarios, the cover plate 70 may include one or more bolt attachments92, such as one or more bolts, to attach the bottom end of the boot sealto the cover plate 70. In doing so, as shown in FIG. 5, the bottom end67 of the boot seal 60 may have a base, such as a flange 68, which hasone or more holes aligned with the one or more bolts 92 of the coverplate 70 to allow attachment of the boot seal 60 to the division 72 withhex nuts screwed onto the bolts 92. Other methods, such as using abracket, as illustrated above, may also be used to attach the boot seal60 to the division 72.

Returning to FIG. 7A, to provide sufficiently strong support forattaching the boot seal, the cover plate 70 may include multiple metalplates stacked together. For example, the cover plate 70 may include twometal plates, which provide a total thickness of about 10 mm. The coverplate 70 can be attached to the division 72 using a clamp 88. Thisattachment is further shown in FIG. 7B. In FIG. 7B, the cover plate 70is attached to the division 72 using a locking bolt 74 and a clamp 88.The locking bolt has a head 86 and is threaded to mate with a thread inan opening of the clamp 74. The division 72 and the cover plate 70 arenow sandwiched between the head 86 of the locking bolt 74 and the clamp88. The locking bolt 74, when tightened, will toggle-lock the coverplate 70 to the division 72. This attachment is simple and permanent. Itis also vibration resistant. It may also accommodate a wide range ofdeck thickness depending on the bolt length. For example, the deckthickness may be in the range from 4 mm to 16 mm or more. The thicknessof the cover plate may be in the range of 10 mm.

In case a cover plate 70 has multiple plates stacked together, all ofthe stacked plates may be sandwiched between the head of the lockingbolt 74 and the clamp 88. Alternatively, as shown in FIG. 7A, a stackedcover plate may have at least a bottom plate and a top plate. The bottomplate of the stack may be attached to the division with a clamp 88, witha top plate on top, whereas the top plate leaves an opening 93 for thehead of the locking bolt 86. Similarly, the top plate may also have oneor more holes aligned with the bolts 92 that are attached to the bottomplate, so that the top plate can be stacked on top of the bottom plate.When the boot seal is placed on top of the cover plate and bolted to thecover plate via the one or more bolts 92 (in FIG. 5), the top plate ofthe stacked cover plate will also be secured to the bottom plate and thedivision.

As shown in FIG. 7C, the firestop system may further include a duct seal78 placed on the cover plate 70 and positioned to cover the opening (98in FIG. 7A) of the cover plate around the bus duct. The duct seal 78 maybe attached to the cover plate 70 by one or more lock tabs 94. In somescenarios, the duct seal 78 may be made of intumescent foam. In order tobe installed surrounding the bus duct, the duct seal 78 may be splitinto multiple sections, which can be joined together. The duct seal 78,when joined together, has an opening that corresponds to the shape ofthe bus duct so that when installed, will form a seal around the busduct 58.

The above illustrated various embodiments provide easy methods ofinstalling the firestop system. For example, a method for installing theillustrated firestop system in FIGS. 5-7 may include placing a bottomcover plate 70 over an opening of the division 72 and attaching thebottom cover plate to the division 72 with one or more clamps 88.Alternatively, and/or additionally, the method may also include fixedlyattaching one or more weld tabs 90 on the division 72 and attaching thebottom cover plate to the division 72 via the weld tabs 90. The bottomcover plate may have a central opening 98 of any size to accommodate theopening of the division 72, in which the bus duct 58 goes through. Forexample, the opening 98 of the cover plate 70 may have a diameter of 250mm. The bottom cover plate may also be split into multiple sectionsthat, when bolted to the division 72, join together to form around thebus duct 58. The method of installing may also include placing a topcover plate over the bottom plate. The bottom plate may have one or morebolt attachments 92, such as threaded bolts, attached thereto, where thethreaded bolts pass through openings in the top cover plate.

The method of installing may also include placing a split intumescentfoam duct seal 78 around the bus duct 58, pushing it down flush with topof cover plates, and engaging the foam seal onto one or more lock tabs94, which are fixedly attached to the cover plate 70. Additionally, themethod of installing may include wrapping a split boot seal 60 aroundthe bus duct 58, where the split boot seal has a sealable split 62, suchas a zipper. The method may further include engaging and closing thezipper 62 to secure the top end 66 of the boot seal 60 to the bus duct58 housing. The method may further include engaging an optional toggle64 attached proximate to the top end 66 of the boot seal 60 to furthertightly secure the boot seal 60 to the bus duct 58. In attaching thebottom end 67 of the boot seal 60, the method may include passing thethreaded bolts 92 on the cover plate 70 through openings at the bottomend 67 of the boot seal 60 (e.g. a base or a flange) and attaching theboot seal 60 to the cover plate 70 using hex nuts.

In the above illustrated embodiments, a boot seal and various othercomponents are disclosed to provide firestopping between a bus duct anda division in which the bus duct goes through. These embodiments provideadvantages in that the firestop system can withstand vibrations asresult of movement of vessel in marine applications. One or morecomponents are disclosed to attach the boot seal to the bus duct and thedivision. Specific materials are also disclosed for various componentsof the firestop system. For example, the boot seal is a thermal barrierwrap, such as microporous insulation loaded with alumina trihydrate, orhigh-temperature fiberglass mat, to allow for heat to escape duringambient conditions while providing firestopping and temperatureresistance under fire exposure conditions. The gasket used for attachingthe top end of the boot seal to the bus duct is an intumescent foamgasket to be able to accommodate irregularities of the bus duct surfaceand thus provide a seal between the bus duct and the top end of the bootseal. These disclosures provide the several advantages of the firestopsystem over traditional firestop system, particularly in marineapplications. However, it should be noted that such materials are merelyillustrative for achieving a desired performance in a desiredapplication. As the application varies, other materials may besubstituted.

Other advantages of the present invention can be apparent to thoseskilled in the art from the foregoing specification. Accordingly, it berecognized by those skilled in the art that changes or modifications maybe made to the above-described embodiments without departing from thebroad inventive concepts of the invention. It should therefore beunderstood that this invention is not limited to the particular examplesand embodiments described herein, but is intended to include allchanges, modifications, and all combinations of various embodiments thatare within the scope and spirit of the invention as defined in theclaims.

The invention claimed is:
 1. A firestop apparatus for fire stopping abus duct that passes through an opening in a division, said apparatuscomprising: a boot seal comprising an insulating material, the boot sealhaving a first end and a second end distal from the first end; the firstend defining a first opening and positioned to surround the bus duct; afirst bracket positioned to surround the bus duct and attach the firstend to the bus duct; a gasket positioned between the first bracket andthe bus duct; the second end defining a second opening larger than thefirst opening; the second end positioned to surround the bus duct andattach to the division; wherein the boot seal is made of flexiblematerial to allow for movement of the bus duct relative to the divisiondue to vibration.
 2. The apparatus of claim 1 wherein the insulatingmaterial is configured to allow heat to escape during ambient conditionswhile providing firestopping and temperature resistance under fireexposure conditions.
 3. The apparatus of claim 2 wherein the boot sealcomprises a thermal barrier wrap or a high-temperature fiberglass mat.4. The apparatus of claim 3 wherein the thermal barrier wrap comprises amicroporous insulation material including at least alumina trihydrate.5. The apparatus of claim 1 wherein the gasket comprises a substantiallyintumescent foam gasket material.
 6. The apparatus of claim 1 whereinthe boot seal comprises a sealable split extending from the first end ofthe boot seal to the second end of the boot seal to allow the boot sealto open and wrap around the bus duct for installation.
 7. The apparatusof claim 6 wherein the sealable split is closeable with a zipper.
 8. Theapparatus of claim 7 wherein the boot seal further comprises a toggleattached thereto proximate to the first end of the boot seal andconfigured to secure the boot seal to the bus duct.
 9. The apparatus ofclaim 8 further comprising a cover plate having a central openingpositioned to surround a cross-section of the bus duct and configured toattach the second end of the boot seal to the division.
 10. Theapparatus of claim 9 further comprising one or more weld tabs positionedto attach the cover plate to the division.
 11. The apparatus of claim 9further comprising one or more clamps, each having a corresponding boltpositioned to go through an opening in the cover plate and an opening inthe division and thread into the clamp so that the cover plate isattached to the division.
 12. The apparatus of claim 11 furthercomprising one of more bolt attachments installed on the cover plate andpositioned to attach a flange of the second end of the boot seal to thecover plate.
 13. The apparatus of claim 12 further comprising a ductseal placed on the cover plate and positioned to cover the opening ofthe cover plate around the bus duct.
 14. The apparatus of claim 13further comprising one or more lock tabs attached to the cover plate andpositioned to lock the duct seal to the cover plate.
 15. The apparatusof claim 1 further comprising a second bracket positioned to attach thesecond end of the boot seal to the division.
 16. The apparatus of claim15 wherein the second bracket has an L-shaped cross-section formed by afirst portion positioned to be attached to the division and a secondportion extending perpendicularly from the first portion and positionedto attach the second end of the boot seal thereto.
 17. The apparatus ofclaim 15 further comprising a sleeve positioned to pass through theopening in the division and also having an opening that allows the busduct to pass through, wherein the sleeve is attachable to the divisionand configured to allow the second bracket to attach thereto to allowthe second end of the boot seal to be secured to the division.
 18. Amethod for fire stopping a bus duct that passes through an opening in adivision, comprising: providing at the opening a boot seal comprising aninsulating material, the boot seal having a first end and a second enddistal from the first end; arranging the boot seal so that the first enddefining a first opening is positioned to surround the bus duct; using afirst bracket positioned to surround the bus duct to attach the firstend of the boot seal to the bus duct; positioning a gasket between thefirst bracket and the bus duct; forming the second end of the boot sealto define a second opening larger than the first opening; arranging thesecond end of the boot seal so that it surrounds the bus duct andattaching the second end to the division; and facilitating vibrationalmovement of the bus duct relative to the division by forming the bootseal of a flexible material.